Magnesium base alloys



UnitedStates MAGNESIUM BASE ALLOYS Derek J. Whitehead, Clifton Junction, Manchester, England, assignor to Magnesium Elektron Limited, Clifton Junction, Manchester, England, a British company No Drawing. Application September 9, 1955 Serial No. 533,494

Claims priority, application Great Britain October 25, 1954 2 Claims. (Cl. 75-168) This invention relates to magnesium base alloys containing 02 to 1 percent zirconium with 0.25 to 6 percent thorium. Rare earth metals may also be included, the quantity however not exceeding 5 percent, and the quantity of thorium and rare earth metals together not exceeding 6 percent. These alloys may also contain up to 4 percent zinc and up to 0.5 percent manganese. Small quantities of other elements which do not precipitate zirconium from solution in molten magnesium base alloy may also be present, although these are preferably omitted. The Zinc content should preferably not exceed about 3 percent. The percentages used herein are percentages by weight of the alloy.

The demand for magnesium base alloys capable of re- Patented Feb. 11,1958

of the alloy. Preferably the proportion of indium is less than 1.0 percent and may usefully be as low as 0.2 percent.

The improvements in corrosion resistance are evident from the following test results:

The following table indicates the eiiects of indium addition on the creep resistance of some of these alloys. Corrosion tests carried out on the same specimens give further evidence of the beneficial efiects of indium o corrosion resistance.

Percent- Creep, Strain, Percent; Corrosion age Stress Temp- Rate, Alloy Indium (T.S.I.) erature, mg./sq.cu1./

added C. 100 500 1,000 day hrs. hrs. hrs.

lug-2.7% Th2.3% Zn0.7% Zr (in 1.5 325 1.05 4.2 accordance with British Patent No. 0.17 1. 5 325 0.59 2.6 733,221). 0. 92 1. 5 325 0. 7O 2. 4 Mg3.2% Th2.1% Zn0.6% Zr0.2% 1 25 350 0. 19 3. 7 Mn (in accordance with British 0. 18 1.25 350 0.25 0.42 0.79 Patent N 0. 759,411). 0. 92 1. 26 350 0. 18 1. 1 2 0 28 taining good mechanical properties (such as resistance to creep) at elevated temperatures has resulted in the development and widespread use of alloys containing small amounts of rare earth metals and zirconium. Such alloys .contain up to about 4 percent rare earth metals together with about 0.7 percent zirconium and may also contain up to about 3 percent zinc. They are generally useful at temperatures up to 250 C. in the sand cast condition. In the further development of magnesium base alloys for service at temperatures up to about 350 C. we have provided alloys of the special compositions described in the specifications of British Patent No. 733,221 and British Patent No. 759,411. The present invention is applicable to all the above types of alloy.

The main object of the present invention is to improve the corrosion resistance of such alloys without any appreciable loss of creep resistance at high temperature. A further object is to achieve even better creep resistance in combination with improved corrosion resistance.

For this purpose we incorporate indium in the alloy in a quantity between 0.01 and 2.0 percent by weight The zirconium content inthe absence of manganese is preferably at least 0.5 percent dissolved in the alloy.

The alloys of the present invention may contain small quantities of other metals for example:

Percent Beryllium up to 0.002 Calcium up to 0.2 Mercury up to 3 Lead up to 1 Thallium up to 1 Lithium up to 3 Tellurium up to 0.1 Silver up to 1 The quantity of beryllium added to the molten alloy may be up to 0.1% or more but this will not result in more than 0.002% in the final alloy.

In alloys according to British Patent No. 733,221 the percentage of thorium is between nine-tenths and three times the percentage of zinc but not exceeding nine-tenths of the zinc content by more than two and three quarters the thorium and zinc together not exceeding 10 percent,

V 3 :I .i' I claim! 1. An alloy consisting of the following:

Percent by weight the percentage of thorium being between nine-tenths and three times the percentage of zinc but not exceeding nine-tenths of the zinc content by more than two and three quarters the thorium and zinc together not exceeding 10 percent.

2. A magnesium base alloy consisting of 0.2 to 1.0 percent zirconium by weight together with thorium 0.25 to 6 percent, by weight, indium 0.01 to 2.0 percent by weight, including at least one of the following additional elements:

4 Rare earth metals Up to 5.0 percent, the quantity of thorium and rare earth metals together not exceeding 6 percent Zinc Up to 4.0 percent by weight Manganese Up to 0.5 percent by weight Beryllium Up to 0.002 percent by weight the balance being magnesium.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Product Engineering, October 1943, pages 630-632. 

1. AN ALLOY CONSISTING OF THE FOLLOWING: PERCENT BY WEIGHT THORIUM -- 1.0 TO 6.0.0 ZIRONIUM -- 0.2 TO 0.9 INDIUM -- 0.1 TO 1.0 ZINC -- 0.5 TO 5.0 MAGNESIUM -- REMAINDERER 